ON THE NEMATODES OF THE COMMON EARTHWORM. 621 
Schneider and the' “ leptoderian ” form of Biitschli are 
clearly distinct and separate species. 
Now Biitschli’s “ leptoderian ” adults are the form 
developed from the larvae living in the worm, as my own 
results have abundantly shown. Schneider’s peloderian ” 
adults, on the other hand, were obtained from worms decaying 
in soil, and were not actually proved to have been developed 
from the larvae inhabiting the worm. Further, while those 
of my cultures of decaying worms, in which all chance of 
contamination from soil larvae has been excluded, have never 
yielded any but the leptoderian species, those, on the other 
hand, in which eairthworms are allowed to decay in ordinary 
soil have, as von Eidanger also (9) has shown, yielded others 
besides the “ leptoderian ” species. Indeed, on one occasion, 
in examining some earth in which several Lumb. terrestris 
had died and decayed, I found a number of larval nematodes, 
from which, when reared in worm extract, I obtained a male 
with a “peloderian ” bursa and the bursal papillae disposed, 
as far as I can judge from a rough drawing’ made at the 
time, similarly to those of Schneider’s form. These con- 
siderations afford sti’ong evidence that Schneider’s ‘^pelode- 
rian ” form was a soil-inhabiting species, attracted while 
larval to the decaying worm, on which it developed and 
matured. This w’ould be quite in keeping with the behaviour 
of the free-living species of nematodes inhabiting the soil, 
studied by Maupas and Potts. 
On this hypothesis the reason why Schneider made the 
mistake of supposing his “peloderian” form to have 
developed from the nematodes inhabiting the worm as larvte 
is not far to seek. Lieberkiihn had seen the larval nematodes 
in the worm develop on the decay of the latter into sexually 
mature adults (which, however, he did not describe), and 
Schneider would naturally suppose, since he did not actually 
make the experiment and prove the contrary, that the adults 
which he himself found on the decaying worm had likewise 
developed from these larvae. In the second place, the reason 
why Biitschli failed to recognise that the form which he des- 
